Flash prefire detector

ABSTRACT

A circuit having indication lights for demonstrating when a flash  trigger pulse has been fed to an X-ray photographic system or the like, is provided. The invention is especially useful in noting that a false triggering pulse, or prefire had inadvertently happened to a flash unit of an X-ray system before it was intended to be used, thus triggering it to photograph, ruining its film. This invention is also useful in that it marks which in a plurality of systems had been the one that had been falsely triggered, and additionally useful in marking that all of the said units had been properly triggered when a true pulsing had been engaged for all units, or of marking which unit had failed to fire.

GOVERNMENTAL INTEREST

The invention described herein may be manufactured, used and licensed byfor the Government for Governmental purposes without the payment to meof royalties thereon.

This application is a continuation of application Ser. No. 573,096,filed Jan. 23, 1985.

BACKGROUND AND FIELD OF THE INVENTION

This invention relates to the field of electrical switching indicationin general and particularly to the field of prefire detection in X-raysystem flash units. A continuing problem in the use of triggered flash,X-ray photography systems is the occurence of a false triggering orprefire. A prefire condition can cause premature exposure of the filmloaded in the X-ray system, and if undetected, results in wasted effortfollowing the time of the prefire. An operator would unwittinglycontinue to take photographic runs with film that had already beenfogged or otherwise prematurely exposed. Those poor runs would result inat least a fogged shot and perhaps a double exposed or likely totallyuseless shot. It is naturally important therefore to reload all the filmcassettes of such a system once the operator has knowledge that aprefire had occured; and it is also quite important to be able to detectsuch occurence of prefire or misfire. In one conventional method todetect prefire and misfire in such photographic systems. A surge on theinput triggering line to the X-ray system is noted by a meter providedin series therewith on the inlet line or in some parallel arrangementtherewith. In this arrangement, the operator must note a sudden dip ordeviation of the meter indicator vane. Noteworthy with this approach isthat the deviation may unfortunately often go totally unnoticed by theoperator. Another convention of mention is to include a flickering lightconnected at the trigger input of the said system which might bearranged to flicker perhaps once during momentary surges or to lightonly during surges. This approach seems better than the meter as far asnoticing the surges, however it still has the disadvantage of theoperator often not noticing the occurrence of the prefire/misfirecondition. The aforedescribed shortcomings become especially serious inthe case of a multiple X-ray system, arranged for photographing a givenscene perhaps in time sequence or possibly simultaneously from differentvantage points instead. As many as thirty different systems might beoperated simultaneously in order to photograph the scene and a prefireof only one of those many systems might not even be noticed amongst allthirty meters or only too briefly in the case of flickering lights. Insuch multi-channel arrays even when a prefire had definitely beennoticed by an operator according to either one of the above-describedmethods, it is not likely he might still recall which of the many unitswas the one that had misfired. The severe shortcomings of not being ableto pinpoint the particular unit having the problem necessitateunfortunately, the reloading each and every one of the units with newfilm with accompanying great amount of wasted time, the wasted cost ofdiscarding perhaps all the film cartridges, and the wasted time inhaving shots of at least one spoiled unit which need retaking causingretake of an entire sequence of shots if a complete test run is thusspoiled. Clearly therefore, it is highly desirable to provide adetection device which would overcome the aforesaid disadvantages andassure the integrity of photographic runs and unexposed film in eachX-ray system.

BRIEF DESCRIPTION OF THE INVENTION

A respective detector circuit is provided for each flash unit in theparticular X-ray system, for which unit it is desired to mark whether ornot it had been triggered. An essential benefit in this invention is tohave a light running steady-on following a triggering, not just during asurge. A lamp is included with each detector circuit, the lighting ofwhich lamp is to signify that the flash unit had been subjected to anoperational pulse such as when it is usually operated. Operation hereincludes either a desired triggering, to mark the unit that had been on,or had an accidental triggering, or a prefire. A lamp is included in thecircuit of the cathode of a suitably biased SCR switching device inseries with a power source, the positive side of which source had beengrounded. The circuit of the anode side of the SCR device is connectedto feed a pulse to a flash unit, through the SCR. The flash power comesfrom the power source but is actually switched on by the SCR guide, byapplying the subject triggering pulse at the cathode gate side of theSCR to switch it on. An R-C discharge circuit with series diode is firstfed by said triggering pulse, to spread the time of the pulse surge andgenerally to build up a voltage sufficient for eventually switching onthe SCR. The SCR after being switched on and thus the lamp too, remainson thereafter until the circuit from the SCR to the flash unit is brokenas by opening switch 108 which is usually left closed but which howeveris opened for purposes of breaking the circuit to shut off the light;the switch is immediately re-closed again after the light goes off inorder to reset the circuit for again marking the next time a triggeringpulse appears. A suitable embodiment for switch 108, for example couldbe a toggle switch, home light switch, even a push button break switch,or a spring loaded normally closed switch. Suitable biasing and feedbackresistor elements for the SCR are provided to enable the SCR to switchat the anticipated voltage levels to be encountered.

OBJECTS OF THE INVENTION

Accordingly, it is an object of this invention to provide means formarking a flash unit of an X-ray system which has been in factpreviously operated so that fresh film may be reloaded therein whereneeded.

Another object is to provide a means of marking which X-ray system, orsystems within relatively a large plurality of similar systems had beenthe ones falsely triggered to operate, so that their film may be changedbefore proceeding further.

Other objects and advantages of this invention will become readilyapparent to those skilled in the art from a reading of the attacheddescription wherein like numerals and captions refer to theircounterparts in the appended drawings in which:

LIST OF FIGURES

FIG. 1 illustrates a plural flash system layout with plurality ofrespective individual detector circuits for marking the occurence of ause of a circuit's respective flasher unit; and

FIG. 2 shows a schematic diagram of one possible embodiment of adetector circuit according to this invention.

DETAILED DESCRIPTION OF THE INVENTION

The above-mentioned features and advantages are accomplished with use ofthe within described invention. FIG. 1 illustrates a multiple bank ofX-ray system flash units 1 through n, 401, 402, . . . , etc. triggeredby a plurality of respective pulses 1 through n, 101, 102, . . . , whichpulses are first made to pass through the added detector units 1 throughn, 201, 202, . . . , etc. of this invention. It is a function of eachdetector unit to provide a steadily-on light device which is brought ONupon the occurrence of a prefire, misfire, or an intentional fire, e.g.Another characteristic of this detector device is that the light willremain on until reset by the operator, this making it likely that theprefire will be discovered. Since each X-ray system has its own detectorunit and each detector unit its own light it is possible to know whichX-ray system it is that has had the accidental prefire in addition tohaving a steady-on indication of such mishap.

In FIG. 2, one embodiment of a detector unit is shown in schematic form.A triggering pulse which would ordinarily be fed directly to an X-rayflash unit 401 is instead fed to it only first by way of a detector unit201. This fairly large, positive going pulse is first passed through adiode unit 112. Diode 112 serves not only to block any negative wavesignals from passing further into the detector circuit, but alsoisolates terminal 101, i.e., it serves to prevent any positive goinglarge voltage surges in the R-C circuit 103, 104 from returning backwardthrough the diode to 101. Thereafter, the full build up of voltage inthe R-C circuit can be used to bias on SCR switch 106, at its terminal 1(cathode gate). It should be noted that the R-C network elongates thesignal to allow enough time for the gate of the SCR device to operate.This permits the full power from the R-C circuit to pass through 106,along the path of switch 108, and appear as signal 109, at outputterminal 301, which passes out to activate flash unit 401. It is assumedthat the X-ray flash unit of the type discussed here without anyspecific type mentioned, may be started by a trigger pulse as small as 9volts such as used here. This is possible for example, because suchunits have low-power level (for safety) switches, operable by humans;the switches are typically connected to internal relays which can handlethe (possible) Kilovolts involved in an X-Ray machine. The high levelvoltage is of course not at the fingertips of the human operator becauseof the great danger, internal relays are used, turned on by low powerlevel, human operated, switches. While such relay(s) is not shown withinthe generalized rectangular box symbolically representing flash unit401, it is understood that commercial X-Ray units employ such switchmethods for remotely turning on the very high power levels of an X-Ray,and that the approximate 9 volt pulse from detector unit 201 will be fedto those locations in the X-Ray machine where a (low power level) switchwould have been turned on by a human, if there had been no detector unitintervening. As such then, the power being made to travel along line 400is only a symbolical way to show that the X-Ray unit is to be turned onby a pulse, following the setting of the detector system. Once the SCRis on, the path through lamp 107 will remain on; i.e. the path ofbattery 110, through lamp 107, SCR 106 from terminal 3 (cathode) toterminal 2 (anode), closed switch 108, line 400 to grounded case of 401,back through the grounded case of 201 to grounded battery 110, remainson by battery power without any further pulses needed at 101. There isno path, at this stage of the operation, that would take one backthrough both lamp 107 and the diode 112, out to terminal 101, becausethere is no longer any pulse at 101 to complete that path. There is somevoltage drop in the SCR from 3 to 2 so that lamp 107 chosen should becapable of operating on less than the full 9 volts in battery 110. Inorder to select the ohmic value of resistor 105, it must be consideredto be of such proportion to the value of resistor 104 so as not topermit the junction 1 to 3 to be biased on without the additional powerof the surge from the R-C circuit 103, 104 caused by the pulse at 101. Agood proportion is at least 1:100 of resistor 105 to resistor 104. Flashunit 401 is merely a block representative of any X-ray system flash unitas described earlier which has a flash type operation tophotographically expose its film during a shot of some desired scene andis in need of an invention of this sort. In the normal operation, aproper firing of the system will of course also trigger the lamp lightin the detector unit to go on. This has the advantage of assuring theoperator that all units have fired properly. However it has thedisadvantage that after each firing of the plurality of X-ray units totake shots it will therefore become necessary to reset all the detectorunits or otherwise perhaps automatically provide therefor. One method ofresetting is of automatically disconnecting the 9 volt power supplyfeeding all detector units after a shot, by other circuitry means notshown, which power off would definitely shut off all the lamps for areset without resort to resetting all the toggle switches of each andevery detector unit. Other switching elements than the shown SCR can beuseful in this type circuit following the principles taught herein; herean ECG-5457 has been used. A listing of circuit element values useful inthe system of FIG. 2 appears below. It is nonetheless stressed howeverthat any elements, values, or even other circuit arrangements whichcould fulfill the basic functions of the intended circuit, wouldlikewise be just as acceptable. The specific elements below are notlimiting, but only exemplary to aid in an understanding of the use ofthis invention.

    ______________________________________                                        Element          Identification                                               ______________________________________                                        112              ECG-177 diode                                                103              0.001 mf.                                                    104              100 KΩ                                                 105              1 KΩ                                                   106              ECG-5457, SCR                                                110              9 volt voltage source                                        107              9 volt lamp                                                  ______________________________________                                    

While the invention may have been described with respect to oneparticular embodiment or embodiments, it should be understood by thoseskilled in the art that the description also includes all equivalents,substitutions and modifications within the spirit and scope of theinvention, the specification or the claims.

What is claimed is:
 1. In an X-ray system having plural flash units forphotographing a subject, the flash units operated by a trigger signal, aflash unit trigger indication system including a plurality of detectorcircuits each one respectively in series with a triggering input to eachsaid X-ray flash unit, each of said detector circuits comprising:an SCRsemiconductor switching device comprising a terminal leading to thecathode gate side of the SCR, at which terminal is fed a triggeringpulse intended for triggering a respective flash unit, the anode side ofthe SCR being connected to the flash unit for passing a triggeringsignal thereto, for initiating its operation for flashing, each of saidflash units being grounded; a positive grounded voltage source; a lampunit connected between the cathode terminal of the SCR and the negativeside of said voltage source, creating an indication in the cathodecircuit path that said SCR has been turned on and operated, and hencethat the voltage source has been fed to trigger a respective flash unitthrough a turned on SCR, a lighting of a respective lamp unit indicatinga triggering of a respective flash unit; a switch connected in seriesbetween each respective flash unit and the anode terminal of the SCR inits respective detector circuit, said switch being opened for turningoff a respective lamp indication in addition to turning off the SCRuntil its next operation.
 2. The indication system of claim 1 whereinthere is further included between the said terminal and cathode gate ofsaid SCR, a series diode and a R-C delay circuit in series therewith,for aid in triggering the said SCR device.